For more than 100 million years marine turtles have covered vast distances across the world's oceans, performing a vital and integral role in marine and coastal ecosystems. Over the last 200 years human activities have tipped the scales against the survival of these ancient mariners. Urgent global action is needed to ensure their future.

Three of the seven existing species of marine turtle are critically endangered

All 7 species of marine turtles are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). 3 are classified as critically endangered by IUCN and a further 3 are classified as endangered.

Many offspring, few survivors

Marine turtles appear to have the potential to reproduce abundantly: females can lay hundreds of eggs in one nesting season. But even under "natural" conditions, relatively few young turtles survive their first year of life.

Predators such as crabs, foxes, and birds often kill the hatchlings as they make their way from the nest to the sea, and when they reach the shallows, many more small turtles are taken by fish.

When humans harvest turtle eggs, disturb or degrade nesting beaches, the scales become tipped even more heavily against young turtles.

Habitat and ecology

Most marine turtle species spend much of their lives in continental shelf waters. Males do not leave the sea and females only come ashore to lay their eggs on sandy beaches during the appropriate season. During the nesting season, mature males and females migrate from feeding grounds and mate near the nesting beach.

Life Cycle

Once the hatchlings exit their nest and reach the sea, a swimming frenzy ensues to reach open ocean zones where currents meet, and where the small turtles find food and refuge from their many predators. Only once marine turtles become adults do they return to the beach area where they were born to lay their own eggs.

Decades to reach maturity

The long time to reach maturity and the many natural dangers faced by hatchlings and juveniles mean that as few as 1 in 1,000 eggs will survive to adulthood.

Current Population and Distribution

5 of the 7 species are found around the globe (mainly in tropical and subtropical waters) while 2 species have relatively restricted ranges: Kemp's ridley occurs mainly in the Gulf of Mexico and the flatback turtle around northern Australia and southern Papua New Guinea.

What are the main threats?

Uncontrolled development has led directly to the destruction of critically important nesting beaches. Lights from roads and buildings attract hatchlings and disorient them away from the sea. Vehicle traffic on beaches compacts the sand and makes it impossible for female turtles to dig nests.

Important marine turtle feeding habitats such as coral reefs and seagrass beds are continuously being damaged or entirely destroyed as a result of sedimentation, nutrient run-off from the land, insensitive tourist development, destructive fishing techniques and climate change.

Hunting and poaching

Hunting and egg collection for consumption are major causes of the drastic decline in marine turtle populations around the world. Green turtles are caught for their meat, eggs and calipee (the green body fat which is the main ingredient in turtle soup).

Researchers estimate that each year poachers take 30,000 green turtles in Baja California and that more than 50,000 marine turtles are killed in Southeast Asia and the South Pacific.

Olive ridley turtles have been pursued for eggs and their skin used for leather production. In the 1960s, over one million olive ridley turtles were butchered each year on Mexico's Pacific coast. In many countries, juvenile marine turtles are caught, stuffed and sold as curios to tourists. Marine turtle eggs are considered an aphrodisiac in some countries and eaten raw or sold as snacks in bars and restaurants.

International trade in products such as tortoiseshell from hawksbill turtles, green turtle calipee and leather from olive ridley turtles has exacerbated the quantity of directed take of marine turtles.

Over the past decades, Japan has emerged as the principal country buying shell (known as Bekko) from tropical countries to produce costly handicrafts. Despite the CITES listing, trade between non-signatory countries and illegal trade persist.

Each year, tens of thousands of olive ridley, Kemp's ridley, loggerhead green and leatherback turtles are trapped in shrimping operations. Marine turtles are reptiles so when they cannot reach the surface to breathe, they drown.

Gill nets and long-line fisheries are also principal causes of marine turtle mortality. Worldwide, hundreds of thousands of marine turtles are caught annually in trawls, on long-line hooks and in fishing nets.

Changing climate and global warming have the potential to seriously impact marine turtle populations. Marine turtles have temperature-dependent sex determination, meaning that an increase in global temperatures could change the proportion of female and male turtle hatchlings and could result in marine turtle populations becoming unstable.

Marine turtles can mistake floating plastic materials for jellyfish and choke to death when they try to eat them. Discarded fishing gear entangles marine turtles and can drown or render a turtle unable to feed or swim. Rubbish on beaches can trap hatchlings and prevent them from reaching the ocean. Oil spills can poison marine turtles of all ages.

Disease

Many types of diseases have been observed in marine turtles. Recent reports of a rise in the occurrence of fibropapillomas, a tumorous disease that can kill marine turtles, is believed to be caused by run-off from land or marine pollution. On some of the Hawaiian Islands, almost 70% of stranded green turtles are affected by fibropapillomas.

Natural predatorsand introduced species

Marine turtles can lay more than 150 eggs per clutch, and lay several times each season, to make up for the high mortality that prevents most marine turtles from reaching maturity. The subtle balance between marine turtles and their predators can be tipped against turtle survival when new predators are introduced or if natural predators suddenly increase in number as a result of human interference.

Circle hooks surround a traditional "J" hook, at centre bottom. The use of large circle hooks and turtle de-hooking devices are proving to be successful in experiments designed to reduce turtle bycatch in longline fishing gear.